79 



therefore we can only account for the changes of climate indi- 

 cated by the organic remains by changes in the relative position 

 of the dry land and the sun's rays. 



Professor Lyell suggested that the changes in the position of 

 land and sea may have given rise to the vicissitudes in climate. 

 The Professor does not bring proofs of more than a mere rise 

 and fall of land from the level of the ocean, which could not 

 furnish us with tropical heat in the arctic regions, therefore he 

 assumes the possibility of geographical changes, such as the 

 shifting of land from the southern hemisphere to the northern, 

 to reconcile the effects with the facts. " However constant/' 

 says the same author, " may be the relative proportion of 

 sea and land, we know that there are constantly some small va- 

 riations in their respective geographical positions, and that in 

 every century the land is in some parts raised and in others de- 

 pressed. By these ceaseless changes the configuration of the 

 earth's surface has been remodeled again and again since it was 

 the habitation of organic beings, and the bed of the ocean has 

 been lifted up to the height of some of the loftiest mountains. 

 The imagination is apt to take alarm when called upon to admit 

 the formation of such irregularities in the crust of the earth after 

 it had once become the habitation of living creatures ; but, if 

 time be allowed, the operation need not subvert the ordinary 

 repose of nature, and the result is in a general view insignificant, 

 if we consider how slightly the highest mountain chains cause 

 our globe to differ from a perfect sphere. Chimboraga, though 

 it rises to more than 21,000 feet above the sea, would be repre- 

 sented, on a globe of about six feet diameter, by a grain of sand 

 less than one-twentieth of an inch in thickness." 



Let us consider what would be the nature of the deposition in 

 a large tract of land like Australia, supposing it gradually floated 

 from its present position to the north polar region. Here and 

 near it, tree ferns, Cycadeae,Araucariae,Cassiarinae grow upon the 

 land : corals and sponges abound on the coast even of Van Die- 

 men's Land ; also Trigonia, Cerithium, Isocardia, a Cardium 

 like C. hillarium of the greensand, and quadrupeds of the pe- 

 culiar marsupial races, to which the Stonesfield animal is re- 

 ferred by Cuvier. These would be deposited, and their place 

 would become gradually occupied by others as it approached 

 the equator, where it would be inhabited by a different variety. 



